Method of fabricating thermometers



Dec. 26, 1950 E. c. ANDRAE METHOD OF FABRICATING THERMOMETERS FiledApril 24, 1946 i Carl Rndrae.

ENTofi RM A' '1 Patented Dec. 26, 1950 METHOD OF FABRICATINGTHERMOMETEES Ernst Carl Andrae, Stockholm, Sweden Application April 24,1946, Serial No. 664,579 In Sweden October .19, 1.944

'7 Claims. (01. 29-1482) dis is well known, a protective gas, mostfrequent-ly nitrogen, is generally introduced into thermometer tubesinstead of atmospheric air, inasmuch as the oxygen of the air is apt tooxidize the mercury and other substances contained therein, the oxidesthus formed soiling the capillary tube and rendering the reading of thethermometer difficult. Hitherto, the filling of the protective gas intothe thermometer tube has only been efiected by mechanical means, thethermometer having been. connected to a gas receptacle and sealed uponhaving been filled with the gas. This is also believed to be the reasonof the fact that hydrogen gas has not been used, which gas wouldotherwise be the most suitable per se owing to its reducing effect. Ifhydrogen would be filled-in in this way, a great risk of explosion wouldbe incurred on account of the possibility of the formation oioxyhydrogen gas.

The present invention refers to a particularly simple and safe method ofintroducing an ar" bitrary protective especially hydrogen, intothermometers and the like. The invention is substantially characterizedby the fact that one or more substances capable of developing the gas inconsideration are introduced into the thermometer tube, whereupon thelatter is sealed by melting.

The accompanying drawing illustrates by way of example three differentstages of the method according to the invention.

Fig. l is an elevational view partly in section of the tube beforeconstriction occurs;

Fig. 2 is an elevational view partly in section of the tube afterconstriction has occurred at one place, and

Fig. 3 is an elevational view partly in section of the tube afterconstriction has occurred at two places.

The capillary tube i, which contains mercury, is provided at the topwith a tubular extension 2 of a much greater internal diameter. Afterthe mercury has been filled-in, a piece of sodium 3 is dropped into thetube 2 (Fig. 1). The latter is then constricted by melting or softeningabove the piece of sodium, as at i, and preferably also at the upper endto such a degree that only narrow openings will remain. Melting orsoftening can be effected by means of a gas flame,and compressed orconstricted by a suitable tool when in the softened condition.Thereafter a small quantity of water 5 is introduced through the upperopening 5 into the tube 2, said Water quantity remaining on account ofits surface tension in or at the opening 4 (Fig. 2). After the water hasthus been introduced, the tube 2 is scaled by .melting at the upper end5 thereof, the Whole being then preferably turned upside down, so thatthe piece of sodium falls down toward the opening l so as to be broughtinto the proximity of the water, although it is not brought into contacttherewith owing to the small diameter of the opening. The water nowevaporates, and the vapour is absorbed by the piece of sodium, so thatsodium oxide and hydrogen are formed. The quantities of water and sodiumare so chosen that the desired pressure, say 25 atmospheres, isobtained. When the tube is then again turned by into its properposition, the piece of sodium oxide generally remains at the opening 4by sticking to the glass wall (Fig. 3).

If desired, the tube may be evacuated or filled with some gas undernormal pressure, for instance with nitrogen, before the hydrogen isintroduced in the manner described, but this is not of any materialimportance, for if the air is caused to remain and the hydrogenintroduced has a pressure of 25 atmospheres, for example, the partialpressure of the oxygen will be less than 1% of that of the hydrogen.

It is also possible first to introduce the water and then the sodium.Instead of sodium, other hydrogen-replacing metals may also be used, itbeing possible generally to make use of a plurality of substances otherthan water and metal, which are capable of developing hydrogen or someother suitable gas on having been introduced into the thermometer or thelike.

Having now described my invention, what I claim as new and desire tosecure by Letters Patcut is:

1. A method of fabricating a thermometer containing hydrogen underpressure wherein a first reactant comprising water and a second reactantcomprising a hydrogen-replacing metal capable of reacting with the waterto form hydrogen are added to thermometer tube, which comprises addingone of the reactants to the tube, con- U stricting the internal diameterof the tube at a point in the tube above the location of said reactant,adding the other reactant into said tube above said constriction,sealing the tube at a point in the tube above the other reactant, andbringing the two reactants into proximity so that the reaction proceedsand the hydrogen is generated in the tube.

2. A method of fabricating a thermometer containing hydrogen underpressure wherein sodium and water are added to the thermometer tubeabove the mercury therein to react with one anwater remaining at saidconstriction in the tube,

sealing the tube at a point therein above the water, and rotating thelongitudinal axis of the tube through 180 whereby the sodium and thewater are brought into close proximity and the reaction.

proceeds to generate hydrogen in the tube.

3. A method of fabricating a thermometer containing hydrogen underpressure wherein sodium and water are added to the thermometer tubeabove the mercury therein to react with one another and form thehydrogen within the tube, comprising adding the water to the tube,constricting the internal diameter of the tube at a point in the tubeabove the location of the water therein, adding the sodium into saidtube said sodium remaining at said constriction in the tube, sealing thetube at a point therein above the water, and rotating the longitudinalaxis of the tube through 180 whereby the sodium and the water arebrought into close proximity and the reaction proceeds to generatehydrogen in the tube.

4. A method in accordance with claim 1 wherein the said tube isevacuated prior to the addition of the reactants.

5. A method in accordance with claim 2 wherein the said tube isevacuated prior to the addition of the sodium thereto.

6. A method in accordance with claim 3 wherein the said tube isevacuated prior to the addition of the water thereto.

'7. A method in accordance with claim 1 wherein air in'the said tube isreplaced by nitrogen prior to the addition of the reactants.

ERNST CARL ANDRAE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,823,452 Heron Sept. 15, 19312,106,495 Debor Jan. 25, 1938 2,361,413 Font Oct. 31, 1944 2,365,285McDill Dec. 19, 1944 2,379,342 Cozzoli June 26, 194-5

